1. Field of the Invention
This invention relates to the field of information displays. In particular, the present invention relates to a system and method for efficiently adjusting display devices.
2. Related Art
Electronic systems and circuits have made a significant contribution towards the advancement of modem society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems have facilitated increased productivity and reduced costs in analyzing and communicating data in most areas of business, science, education and entertainment. Frequently, these electronic technologies are utilized to convey information. Displaying information in a visual presentation is usually a convenient and effective method of conveying the information. However, poor quality or distorted displays typically impede information presentation and user comprehension. There are a number of conditions that adversely effect the performance of the display components and interfere with the presentation of information.
Numerous electronic systems and devices are utilized to convey information. For example, computer systems typically include a display monitor for displaying information. Display devices such as cathode ray tube (CRT) devices and field emission display (FED) devices usually generate light by impinging high-energy electrons on a picture element (pixel) of a phosphor screen and the phosphor converts the electron energy into visible light. The emitted light is utilized to convey images to observers and the properties of the emitted light have a significant impact on the perceptibility of the presentation. Typically, the greater the light emission the greater the presentation clarity.
Different types of displays such as cathode ray tubes (CRTs) and field emission devices (FEDs) usually differ in the manner in which the high energy electrons are impinged on a pixel. Conventional CRT displays typically use a single electron beam, or in some cases three electron beams, to scan across the phosphor screen in a raster pattern. FEDs usually utilize stationary electron beams for each color element of each pixel, enabling the distance from the electron source to the screen to be very small compared to the distance required for the scanning electron beams of a conventional CRT. In addition, the vaccum tube of the FED is usually made of much thinner glass and consumes less power than a conventional CRT.
The performance of components in field emission displays is usually impacted by a variety of conditions. FED devices rely upon a predetermined relationship between current utilized to drive illumination and the emission characteristics of a pixel. The FED devices are usually driven with a predetermined voltage designed to result in a particular current that produces a particular display intensity. However, various conditions (e.g., temperature changes) can have an adverse impact on FED components over time, such as changes in emission characteristics that alter the relationship between drive current and illumination. For example, at one time a FED may be driven with a specific amount of voltage resulting in a specific current and at some later time when driven at exactly at the same drive level voltage, the current is something different due to emission characteristic changes. Since the amount of current ultimately determines the brightness of a display presentation, displays typically get brighter or dimmer over time, depending upon the nature of the changes that occur to the components (such as at the cathode). The effects of these detrimental environmental conditions often adversely impact the presentation of information and images on a field emission display.
Traditional attempts at compensating for adverse environmental conditions, such as measuring temperature at a cathode, often encounter difficulties. For example, compensating for thermal lags that do not permit measurement in real time often poses problems. Another problem with traditional approaches is they are often limited in scope. For example, limiting an attempt to temperature measurement typically does not address other adverse conditions, such as emission deterioration caused by contamination. If some other mechanism other than temperature is causing problems, it is very difficult to detect the problem if the temperature remains stable throughout the changes.
What is required is a system and method for monitoring FED performance and compensating for adverse impacts on display emission generation.
The present invention is a system and method for monitoring field emission display (FED) performance and compensating for adverse impacts associated with display emission generation. A present invention FED adjustment system and method is capable of providing real time emission characteristic monitoring during retrace periods. In one present emission compensation method, a feedback type process is utilized that drives a constant voltage level on test pixels not included in the active viewing area and compares the results (e.g., the current or illumination that is associated with the emission) to an expected predetermined result (e.g., amount of current or illumination). For example, if a measured parameter (e.g., illumination, current, etc.) associated with the test pixel is too high then the voltage supply is reduced on the drive level or if the measured parameter is too low the voltage is increased. In one embodiment of the present invention, a driver voltage is supplied and an image is presented in an active pixel region during an active presentation time. Emissions are produced in a test pixel during a nonactive presentation time and a determination is made if the emissions in the test area are accurate. If the emissions are not accurate, adjustments to the pixels are made to provide a desired level.